Hydraulic control for dies in ram type presses



Aug. 23, 1966 F. M. WILLIAMSON HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSES 4 Sheets-Sheet 1 INVENTOR.

Filed Oct. 16, 1961 Aug 23, 1955 F. M. WILLIAMSON 3,267,715

HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSES Filed Oct. 16, 1961 4 Sheets-Sheet 2 I NVEN TOR.

Allg- 23, 1956 F. M. wlLLlAMsoN 3,267,715

HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSES Filed OGL` 16, 1961 4 Sheets-Sheet 3 I Kga; (5&4

IINVENTOR. f1 [dra/.47 MH/zZZZd/rfsa/z 1 -EA; @WM/247% ug- 23, 1966 F, M. wlLLlAMsoN 3,267,715

HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSES Filed Oct.. 16, 1961 4 Sheets-Sheet 4 l NVENTOR. 7/0567 M m'Z/Z'd/yfsa/Z United States Patent C;

3,267,715 HYDRAULHC CONTRQL FOR DIES 1N RAM TYPE PRESSES Floyd M. Williamson, Detroit, Mich., assigner, by mesne assignments, to Di-Di'o Engineering Company, Detroit, Mich., a corporation of Michigan Filed st. 16, 1961, Ser. No. 145,297 6 Claims. (Cl. 72-351) This invention relates to hydraulic controls for dies in ram type mechanical presses and has particular reference to certain improvements in hydraulic cushions for such presses of the type disclosed in my earlier Patents 2,901,238 and 2,938,718, and in my prior copending application Serial No. 114,264, filed June 1, 1961, issued as Patent No. 3,124,340, for Hydraulic Control for Die Pads in Presses, the present application being a continuation-in-part of such prior copending application.

More particularly the present invention is directed to a hydraulic control system incorporationg means to advance or elevate a forming portion of a die in synchronism or in sequence with the movement of other movable sections of the die, or independently of movement of other sections of the die, during the cycle of press operation. This arrangement may be employed to expedite stripping of the work from the die as well as for work forming operations whereby a crank type press incorporating this invention may be operated at a substantially increased rate.

Accordingly, an object of the invention is to provide a new and improved hydraulic control for dies in ram type presses.

Another object of the invention is to provide a new and improved hydraulic die cushion for ram type presses.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are four sheets, which 'by way of illustration show preferred embodiments of the invention and what I now consider to be the best mode of applying the principles thereof. Other embodiments of the invention may be used without departing from the scope of the, present invention as set forth in the appended claims.

In the drawings:

FIG. 1 is a schematic illustration of a crank type press embodying the invention;

FIG. 2 is a schematic view of t'ne type shown in FIG. 1 and illustrating a modification of the invention;

FIG. 3 is a fragmentary side elevational view of a crank type press, partly in section, and showing a modified form of the invention;

FIG. 4 is a fragmentary View of a crank type press embodying a further modification of the invention;

FIG. 5 is a schematic View illustrating a further modification of the invention; and

FiG. 6 is an enlarged fragmentary sectional View taken along the line 6 6 of FIG. 5.

As illustrated in FIG. 1, a ram type mechanical press embodying the invention includes a ywheel 10 mounted on the crank 12 of the press to rotate therewith, a ram 14 which is reciprocated by the crank of the press, and a bolster 16 on which dies 18 and 20 are mounted. A punch 22 mounted on the ram 14 upon the descent of the ram is adapted to engage a sheet of metal positioned on the dies 18 and 2i) and to clamp such sheet between the punch 22 and the die 20. The punch 22 is shown in its extended position and as it moves down during the closing movement of the press ram the outer peripheral edge 24 is cooperable with the. inner peripheral edge 26 of the die block 28 to shear a work blank from the sheet and to frictionally clamp the periphery of such blank against the 3,267,715 Patented August 23, 1966 upper surface of the die as the die 2G moves down with the punch 22.

The die 18 as illustrated comprises a circular forming post which is disposed within the annular die 20. The die 18 is seated on the upper surface of a cylinder 30 which in turn is clamped by the bolster section 16 to the upper surface of the lower bolster section 32. As the punch 22 descends, a second punch 34 mounted on the ram 14 cooperates with the upper portion of the die 18 to form the blank into the desired form, such as the cup or cap 36. The punch 34 is movable relative to the punch 22 and is biased to its extended position by a spring 38. A spring pressed pressure plate surrounds the punch 22 and is engageable with the sheet of material from which the blank is sheared to clamp the sheet against the upper surface of the block 28 during the opening and closing movement of the press ram.

The die 2t) is reciprocably mounted in the die block 28 and is shown in its advanced or extended position which is determined by engagement of the shoulder 42 on the die 20 with the internal shoulder 44 on the die block 28. Under the pressure of the punch 22 the die 20 moves downward against a hydraulic cushion which biases the die Ztl to its extended position and provides the pressure against which the punch 22 reacts during the closing of the press ram.

One or more rods 46 at their upper ends react on the die 20, and at their lower ends on a two-stage piston 48 which comprises a large diameter piston 5() which works in the hydraulic pressure cylinder 52 and a small diameter piston 54 which works in the high pressure hydraulic cylinder 56. A tank 58 containing hydraulic fluid under pressure is connected by a hydraulic fluid pressure transmitting connection 60 to the cylinder 52 whereby pressure of the fluid in the tank 58 is transmitted to the piston S0 so as to react on the rod 46 and bias the die 20 to its extended position. The tank 58 contains hydraulic fluid under a regulated pressure of the order of 100 lbs. per square inch. Hydraulic uid pressure is also transmitted from the tank 58 through a hydraulic fluid pressure transmitting connection 62, 64 and a valve 66 to the high pressure cylinder 56 to react on the piston 54 therein for `biasing the die 20 to its extended position. The hydraulic uid pressure transmitting connection 62, 64 passes through a pressure relief valve indicated generally at 66 and includes intersecting passages 68 and 70 having a check valve 72 therein which permits the unrestricted ow of hydraulic fluid under pressure from the line 62 through the passage 68 past the check valve 72 and through the passage into the line 64. This forms a by-pass around the normally closed pressure regulating valve 74 which will open when the pressure in the cylinder 56 and the line 64 rises above the pressure for which the valve 74 is set so as to permit the displacement of hydraulic fluid from the cylinder 56 under the control of valve 74.

From the foregoing it will be evident that the pressure in the tank 58 will react on the piston 50 to resist downward ymovement thereof, while the downward movement of the piston 54 will be resisted -by the resistance created in the line 64 by the pressure regulating valve 74. This resistance will be substantially greater than the resistance afforded by the pressure in the tank 58. Thus the high pressure cylinder and piston 54, S6 provide the required resistance to retraction of the die 20 upon the closing of the press while the larger diameter piston 50 assists in returning the die 2t) to its extended position to strip the Work from the die `Preferably the pressure regulating valve is of the type 'of construction illustrated in my prior Patent No. 2,938,718 or No. 2,901,238.

As above indicated, the die 18 is shown in its retracted position seated on the upper end of the cylinder 3l). Integral with the die 18 is a piston 80 which works in the aast/,715

er Cylinder bore 32 internally provided in the cylinder 3i). A spring 3d!- contined `between the piston and a shoulder provided at the upper end of the cylinder bore 82 biases the die iii to its retracted position as shown. The lower end of the cylinder bore 32- is connected by hui-d pressure line 26 to a valve indicated generally at which in turn is connected by duid pressure line 9@ to the manifold S2 that leads to the lower end of the tank 58. The line 9d communicates with a cylinder fiilin the valve Sii, the lower end of which is connected by passage 96 to the line S6 whereby hydraulic iluid under tank pressure is supplied to the lower end of the cylinder Vbore 32 to react on the piston 3d. However, the pressure thus provided is insuiiicient to overcome the spring and hence the die l@ normally remains seated on the upper surface of the cylinder 3u. The line 9G communicates with a passage 9S in the valve 83 which intersects a passage itl@ which communicates with a line 102 that in turn communicates with a high pressure cylinder fr-ft, whereby hydraulic duid under tank pressure is supplied to the cylinder ldd. A check valve lilo in the line permits tree ow from the line 9S into the line lit@ while preventing reverse how. The line llZ communicates with the upper end of the cylinder 94:-, as does the end of the line A piston type valve iti slidable in the cylinder 94s is biased by a spring ilu so as to close the port through which the line 85 communicates with the cylinder 94, as well as the port through which the line idf/2 communicates with the cylinder 4. A piston lZ which works in the cylinder itl-tcarries a roller iid which is biased by means of spring llo and arm M8 against the outer surface of the Cam 126 xed to the crankshaft i2 to rotate therewith. As the press cycles, the high point on the cam reacting on the roller iid will advance the piston 112 in the cylinder 164, thereby to discharge hydraulic fluid under high pressure to the line itil and to valve 88. rihis will iirst shift the valve 198 so as to establish communication through the cylinder 9ebetvveen the lines lill and `86 and then to close oi the inner extremity of line 50, thereby forcing hydraulic fluid under high pressure into the .cylinder bore 82 and advancing the die i3. The upward motion of the die 1S relative to the die 2li will strip the formed work 36 from the die 2li. After the high point of the cam ypasses the roller lit-t, the high pressure in the cylinder itil-.l will be released and the pressure in the tank 58 will be efective to recharge the cylinder lill?. The release of the high pressure in the cylinder idd will permit the spring :titi to return the valve idd to its position as illustrated, thus closing the port leading to line 86 and opening the port leading to line 9d, thus permitting the discharge of hydraulic fluid from the cylinder bore `SZ under the inlluence of spring 8d and re raction of die 18.

The cam il@ can be xed at various positions on the crank shaft, depending upon when it is desired to elevate the die 18 to strip the work from the die E@ The carn 12d may be set so as to advance the die Il?) simultaneously with the closing of the press ram or prior thereto.

In the simplied arrangement schematically illustrated in FIG. 2 the large diameter cylinder and piston 52, 50, the valve S3, and the hydraulic pressure means operable by the crank of the press for moving the die ld toward an extended position have been eliminated. Thus in the hydraulic control system of FIG. 2, hydraulic fluid under tank pressure is supplied through the line 2d@ past the check valve 201 to the line 2.@2 which communicates with the high pressure cylinder 164i having a piston iti?. therein operated by a cam l2@ on the crankshaft i2, as per FIG. 1. The die Zt) may be the same as in FIG. l, whereas the central die M8 is xed upon the upper end of a base 265 mounted upon the die block 32. The cylinder 56 and piston 54 in this case provide the hydraulic cushion for the die 20 and the cylinder 56 is connected through valve de with the tank or pressure fluid 5S in the same manner as in FIG. l. However, in this case the high pressure cylinder reu.) is connected kby line 202 to the cylinder Se via the line 61.1, a check valve 2de being included in the line 282 to prevent return dow of hydraulic huid through the line 202 to the cylinder 154i when the piston iid is subjected to pressure due to the closing or" the press ram. Thus the high pressure cylinder iti-'l is employed to supply high pressure fluid to the cylinder S6 so as to apply pressure to the piston 5d for stripping purposes substantially in excess of the pressure supplied from the tank 58.

in the modication shown in FlG. 3 the piston i12 of the high pressure cylinder 'idd is actuated by a crank and pitman indicated generally at 39d ymounted on the crankshaft i2 instead of the cam 126 as shown in NGS. l and 2. The line Titi?, communicating with the high pressure cylinder N21i is hooked up with the tank 53 by means of a valve 88 as shown in FlG. l. ln this modification the die 2113 is movable relative to the die 2i? but in a somewhat different fashion; that is, in FIG. 3 the die 2i?, is biased to its extended position as shown by a hydraulic cushion which includes the hydraulic cylinder 392 in which there is disposed a piston 3M which moves with the die 2id. The cylinder 392 is connected to the valve 8S by a `line 36 in the same way in which the cylinder 2 is connected to the valve 88 yby the line 86 in FlG. l. Thus the pressure normally reacting on the die 2l3 to maintain it in its extended position is the tank pressure, while the pressure developed in the high pressure cylinder ldd is supplied to the cylinder G02 to react on the piston 3M, for advancing the die 2li; for stripping purposes. The die @it is backed up by a hydraulic cushion `which is the same as that illustrated in -FIG. 1.

in the arrangement illustrated in FIG. 4 the high pressure cylinder ldd is mounted on a bracket on the upper end of the press, and the piston ill thereof is actuated by a crank and pitrnan arrangement like that shown in FIG. 3, but in this case the crank is mounted on a shaft 3(96 of a gear 3% which is driven `through a pinion 31h from a gear 3M rotatable with the fly-wheel of the press. it will be understood that any of the arrangements illustrated in FlGS. 2, 3 and 4 may be employed rfor energizing the thigh pressure cylinder liti-fi.

Thearrangernent illustrated in FIGS. 5 and 6 is in many respects like that illustrated in FIG. l except that the large diameter cylinder and piston 52, Si? have been eliminated and instead of having a single high pressure cylinder libel energized by the rotation of the crank shaft, a double cylinder arrangement is employed, one to supply high pressure fluid to the cylinder 82 as in FIG. l and for advancing the die i8, and the other for suppiying high pressure huid to the small diameter piston 56 as in FIG. 2 for stripping purposes. Thus the die 18 is mounted and arranged as in FIG. 1 and the cylinder S2 thereof is connected to the tank Sand to a high pressure cylinder l0-4 exactly as illustrated in FlG. l. The axis of the cylinders the, however, is oriented diierently since it is a part of a double piston and cylinder arrangef ment which will be subsequently described.

The small diameter cylinder 56 which together with the piston 5d provides the hydraulic cushion for the die 2t?, as in FlG. 2, is connected to the tank 5h through the pressure regulating valve and to a high pressure cylinder liti-texactly as illustrated in FIG. 2, whereby high pressure fluid from the second cylinder 'N4 may be supplied through the line 262 and the line 64 to the cylinder S for reacting on the piston 5d to provi-de additional pressure for stripping purposes.

Each of the high pressure cylinders 164 includes a piston like the piston M2, and such pistons are interconnected `by a rod 32d, a portion of which is straddled by a bifurcated arm 32,2. The ar-rn 322 is carried by a rocker 32d arranged to pivot on pin 326. The rocker carries a roller 32S cooperable with a cam 33d and another roller 332 cooper-able with a second cam 334, the cams 33u and 334- being mounted upon an extension of the crankshaft 12 whereby the rocker 324 will energize the cylinders 104. The cams 330 and 334 may be adjusted relative to each other, the object being to energize the high pressure cylinders 104 at the desired time to provide the high pressure fluid to the cylinder bore 82 and to the cylinder 56 so as to secure the desired movement of the dies 1-8 and 20.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a crank itype press having a plurality of dies engageable with a `work blank, one of said dies being movably mounted and disposed so as to be moved relative to the other die from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, a hydraulic cushion for said one of said dies to resist such movement thereof and to effect return movement of said ldie to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable with said one of said dies, a tank containing hydraulic fluid under pressure, a hydraulic fluid pressure transmitting connection between said tank and said hydraulic pressure cylinder whereby pressure 0f the fluid in said tank is transmitted to said piston so as to bias said one of said dies to its extended position, a nor- -mally closed pressure relief valve in said connection to provide a predetermined resistance, substantially greater than tank pressure, to Aiiofw of hydraulic iiuid from said hydraulic -pressure cylinder due to movement of said piston in said hydraulic pressure cylinder upon closing of the press ram, said other of said dies being positioned to engage and hold a portion of the work blank while the punch on the ram and said one of said dies draw the Work blank thereover, and hydraulic pressure means operable by the crank of the press for generating hydraulic pressure substantially greater than tank pressure for moving one of said dies toward an extended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic fluid thereto at a pressure higher than that of the hydraulic uid supplied through said connection from said tank.

2. In a press a die engagea-ble with a work blank mova'bly mounted and disposed so as to be move-d from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, a hydraulic cushion for said die to resist such movement thereof and to effect a return movement of said die to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable with said die, a tank containing hydraulic `liuid under pressure, a hydraulic liluid pressure transmitting connection between said tank and said hydraulic pressure cylinder whereby pressure of the fluid in said tank is transmitted rto said Ipiston so yas to bias said die to its extended position, a normally closed pressure relief valve in said connection to provide a predetermined resistance to tiow of hydraulic uid from said hydraulic pressure cylinder due to movement of said piston in said hydraulic pressure cylinder upon closing of the press ram and hydraulic pressure means operable by the crank of the press for moving said die torward an extended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic fluid thereto at a pressure higher than that of the hydraulic iiuid supplied through said connection for said tank.

3. In a press a die engageable with a work blank movably mounted and disposed so as to be move-d from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, a hydraulic cushion for said die to resist such movement thereof and to effect a return movement of said die to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable with said die, a tank containing hydraulic fluid under pressure, a hydraulic fluid pressure transmitting connection between said tank and said hydraulic pressure cylinder Iwhereby pressure of the lluid in said tank is transmited to said piston so as to bias said die to its extended position, and hydraulic pressure means operable by the crank of the press for moving said die toward an extended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic iluid thereto at a pressure higher than that of the hydraulic uid supplied through said connection from said tank.

4. In a crank type press having a plurality of dies engageable with a work blank, one of said dies being movably mounted and disposed so as to be moved relative to the other die from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, a hydraulic cushion for said one of said dies to resist such movement thereof and to effect return movement of said die to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable With said one of said dies, a tank containing hydraulic uid under pressure, a hydraulic uid pressure transmitting connection between said tank and said hydraulic pressure cylinder whereby pressure of the iluid in said tank is transmitted to said piston s0 as to bias said one of said dies to its extended position, a normally closed pressure relief valve in said connection to provide a predetermined resistance, substantially greater than tank pressure, to ow of hydraulic iluid from said hydraulic pressure cylinder due to movement of said piston in said hydraulic pressure cylinder upon closing of the press ram, said other of said dies being positioned to engage and hold a portion of the work blank while the punch on the ram and said one of said dies draw the Work blank thereover, and hydraulic pressure means operable by the crank of the press for generating hydraulic pressure substantially greater than tank pressure for moving said one of said dies toward an extended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic uid thereto at a pressure higher than that of the hydraulic uid supplied through said connection from said tank including a high pressure cylinder, a piston reciprocally received within said Cylinder, a pivotally mounted lever, a roller rotatably secured to one end of the pivotally mounted lever in contact with said piston, a cam secured to the crank of said press engaged with said roller and resilient means operable on the lever for urging the roller into contact with the cam.

5. In a crank type press having a plurality of dies engageable with a work blank, one of said dies being movably mounted and disposed so as to be moved relative to the other die from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, ra hydraulic cushion for said one of said dies to resist such movement thereof and to eiect return movement of said die to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable with said one of said dies, a tank containing hydraulic fluid under pressure, a hydraulic fluid pressure transmitting connection between said tank and said hydraulic pressure cylinder whereby pressure of the fluid in said tank is transmitted to said piston so as to bias said one of said dies to its extended position, a normally closed pressure relief valve in said connection to provide a predetermined resistance, substantially greater than tank pressure, to ow of hydraulic fluid from said hydraulic pressure cylinder due to movement of said piston in said hydraulic pressure cylinder upon closing of the press ram, said other of said dies being positioned to engage and hold a portion of the work blank while the punch on the ram and said one of spew/1s said dies draw the work blank thereover, and hydraulic pressure means operable by the crank of the press for generating hydraulic pressure substantially greater than tank pressure for moving said one of said dies toward an extended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic iluid thereto at a pressure higher than that of the hydraulic fluid supplied through said connection from said tank including a high pressure cylinder, a piston reciprocally mounted in said cylinder and a crank and pitman connected between the piston and press crank for reciprocating said piston within said cylinder on actuation of said press.

6. ln a crank type press having a plurality of dies engageable with a work blank, one of said dies being movably mounted and disposed so as to be moved relative to the other die from an extended to a retracted position by a punch on the press ram upon the closing of the press ram, a hydraulic cushion for said one of said dies to resist such movement thereof and to elect return movement of said die to its extended position upon opening of the press ram, said hydraulic cushion comprising a hydraulic pressure cylinder having a piston therein movable with said one of said dies, a tank containing hydraulic luid under pressure, a hydraulic iluid pressure transmitting connection between said tank and said hydraulic pressure cylnder whereby pressure of the fluid in said tank is transmitted to said piston so as to bias said one of said dies to its extended position, a normally closed pressure relief valve in said connection to provide a predetermined resistance, substantially greater than tank pressure, to flow of hydraulic fluid from said hydraulic pressure cylinder due to movement of said piston in said hydraulic pressure cylinder upon closing of the press ram, said other of said dies being positioned to engage and hold a portion of the work blank while the punch on the ram and said one of said dies draw the Work blank thereover, and hydraulic pressure means operable by the crank of the press for generating hydraulic pressure substantially greater than tank pressure for moving said one of said dies toward an eX- tended position connected to said hydraulic pressure cylinder of said hydraulic cushion for supplying hydraulic fluid thereto at a pressure higher than that of the hydraulic fluid supplied through said connection from said tank including a high pressure cylinder, a piston reciprocally mounted in said cylinder, a gear connected to be rotatable with the crank of the press, a pinion engaged with the gear, a second gear engaged with said pinion for rotation thereby and a crank and pitman structure connected between the second gear and the piston for reciprocating said piston in said cylinder on rotation of said second gear.

References Cited by the Examiner UNITED STATES PATENTS 1,697,611 1/1929 Rode 113-46 1,772,914 8/1930 Rode 267-1 2,403,912 7/1946 Doll 267-1 2,842,357 7 195 8 Williamson 113-46 2,93 3,307 4/ 1960 Williamson a 113-46 3,085,530 4/1963 Williamson 72-351 3,124,340 3/1964 Williamson 113-46 CHARLES w. LANHAM, Primary Examiner.

NEDWN BERGER, Examiner.

K. A. COCKS, R. 3. HERBST, Asssmlzt Examiners. 

1. IN A CRANK TYPE PRESS HAVING A PLURALITY OF DIES ENGAGEABLE WITH A WORK BLANK, ONE OF SAID DIES BEING MOVABLY MOUNTED AND DISPOSED SO AS TO BE MOVED RELATIVE TO THE OTHER DIE FROM AN EXTENDED TO A RETRACTED POSITION BY A PUNCH ON THE PRESS RAM UPON THE CLOSING OF THE PRESS RAM, A HYDRAULIC CUSHION FOR SAID ONE OF SAID DIES TO RESIST SUCH MOVEMENT THEREOF AND TO EFFECT RETURN MOVEMENT OF SAID DIE TO ITS EXTENDED POSITION UPON OPENING OF THE PRESS RAM, SAID HYDRAULIC CUSHION COMPRISING A HYDRAULIC PRESSURE CYLINDER HAVING A PISTON THEREIN MOVABLE WITH SAID ONE OF SID DIES, A TANK CONTAINING HYDRAULIC FLUID UNDER PRESSURE, A HYDRAULIC FLUID PRESSURE TRANSMITTING CONNECTION BETWEEN SAID TANK AND SAID HYDRAULIC PRESSURE CYLINDER WHEREBY PRESSURE OF THE FLUID IN SAID TANK IS TRANSMITTED TO SAID PISTON SO AS TO BIAS SAID ONE OF SAID DIES TO ITS EXTENDED POSITION, A NORMALLY CLOSED PRESSURE RELIEF VALVE IN SAID CONNECTION TO PROVIDE A PREDETERMINED RESISTANCE, SUBSTANITALLY GREATER THAN TANK PRESSURE, TO FLOW OF HYDRAULIC FLUID FROM SAID HYDRAULIC PRESSURE CYLINDER DUE TO MOVEMENT OF SAID PISTON IN SAID HYDRAULIC PRESSURE CYLINDER UPON CLOSING OF THE PRESS RAM, SAID OTHER OF SAID DIES BEING POSITIONED TO ENGAGE AND HOLD A PORTION OF THE WORK BLANK WHILE THE PUNCH ON THE RAM AND SAID ONE OF SAID DIES DRAW THE WORK BLANK THEREOVER, AND HYDRAULIC PRESSURE MEANS OPERABLE BY THE CRANK OF THE PRESS FOR GENERATING HYDRAULIC PRESSURE SUBSTANTIALLY GREATER THAN TANK PRESSURE FOR MOVEING ONE OF SAID DIES TOWARD AN EXTENDED POSITION CONNECTED TO SAID HYDRAULIC PRESSURE CYLINDER OF SAID HYDRAULIC CUSHION FOR SUPPLYING HYDRAULIC FLUID THERETO AT A PRESSURE HIGHER THAN THAT OF THE HYDRAULIC FLUID SUPPLIED THROUGH SAID CONNECTION FROM SAID TANK. 